Ph.D. / Applied Physics & Electronic Science / Direct detection, photon counting receivers for use in optical communication through the clear air, turbulent atmosphere have been examined. In particular, spatial diversity arrays to overcome the effect off adding due to atmospheric turbulence are considered. Experimental results are compared with theoretical results for an optimum receiver structure based upon Bayes criterion of minimum probability of error. In addition, certain suboptimum receivers with simpler structures are derived directly from the optimum receiver. These receivers, along with an adaptive threshold receiver, are considered in order to examine the trade off between performance and complexity. The results indicate that the adaptive threshold receiver is a good compromise for information rates that are high with respect to scintillation frequencies, a relatively unrestrictive condition.

A unique tool is developed that allows the user to model physical representations of complicated glovebox facilities in two dimensions and determine neutral-particle flux and ambient dose-equivalent fields throughout that geometry. The code Pandemonium, originally designed to determine flux and dose rates only, has been improved to include realistic glovebox geometries, time-dependent source and detector positions, time-dependent shielding thickness calculations, time-integrated doses, a representative criticality accident scenario based on time-dependent reactor kinetics, and more rigorous photon treatment. The photon model has been significantly enhanced by expanding the energy range to 10 MeV to include fission photons, and by including a set of new buildup factors, the result of an extensive study into the previously unknown "purely-angular effect" on photon buildup. Purely-angular photon buildup factors are determined using discrete ordinates and coupled electron-photon cross sections to account for coherent and incoherent scattering and secondary photon effects of bremsstrahlung and florescence. Improvements to Pandemonium result in significant modeling capabilities for processing facilities using intense neutron and photon sources, and the code obtains comparable results to Monte Carlo calculations but within a fraction of the time required to run such codes as MCNPX.